We evaluated initial BMI data from a longitudinal pediatric cohort study (to run from 1/1/07 to 12/31/12) based on electronic medical record (EMR) data of children (3-11 yr) and adolescents (12-17 yr) from 3 large US health plans. Current data are available on 244,523 subjects through 12/31/09. We collected longitudinal and cross-sectional data from clinic records including gender, age, race, height, and weight. Body mass index (BMI) percentiles were calculated using height, weight, gender, and age, based on the CDC established reference growth charts. We report here BMI percentile, based on single measures. The cohort consists of 244,523 subjects (58.3% 3 -11 years of age, 41.7% 12-17 years, and 50.1% female). We report the proportions of children and adolescents having initial clinical measurements that meet or exceed the 85th BMI percentile of BMI at time of entry into the cohort (Table). Measures collected at the initial clinical visit indicate high levels of overweight in all age categories, including age 3-5 years, confirming that effective public health and clinical strategies to mitigate overweight and prevent type 2 diabetes need to reach children below age 6 and possibly below age 3. Further analysis will provide additional insight on persistence of elevated BMI percentile over time, and elucidate the impact of BMI on glucose metabolism, BP, and other cardiovascular risk factors.